Latch bolt



United States Patent messed Charles A; Ellis, Hamden, Grimm-Mailer (b Sargent &

Company, New flaven comia incorporation of Connecticut Application March 9;,1955, Si-l'al Ne. 495M157 1 Claim. enum rat This invention relates to latch seas, and more particularly to the constructionofthe' ad eflatiih bolt Whereby the effort required to retract the! ab ngagernent of the latch bolt head'with tlie eraser a user is greatly reduced. p

It is usual to provide a noerwi'tha latch bolt haviiig a beveled face so that when the isfclosfd, tliisface engages a strike plate andllie bolfiscalilrned rearwardly to a retracted position within the I se tii perrriil the full closing of the door; As the clam 'fbrcei is applied at right angles to the movement of'the-latchbclgtlie beveled face of the bolt only resolves a component'ofthis'force in the direction of the rnov'e eht ofltli Thus it requires a considerable elforttd'fetra ct-t eboltdiie-irl' a large part to the friction between the back or looking surface of the bolt and the edgeof the opening in the face late of th ease throughvfvhich the bolt slides.

It is contemplated by'th'e resent invention to reduce the friction between the moving parts, and thusreduce the effort required to retract the latch whenthe door'isfclosed. Also it has been found that the closingjeffort required for a new bolt is appreciably less than one that hasbeen used for a considerable length of time, and the constructionof the latch bolt of the present application is such that there is very little increase in the required closing effort even after long use of the bolt.

This result is achieved by providing the latch bolt with a groove or recess extending entirely around the bolt head except at the back thereof adjacent the stem. This groove even extends part way around the back, as will be later explained. An insert of a wear-resisting and low friction material is placed in this groove, the insert being of slightly greater thickness than the depth of the groove so that it will project slightly from the striking surface and also the locking surface of the bolt head in order that the material of the insert will be the only part of the bolt head which will be engaged by the adjacent parts of the lock case or the door strike. Moreover, the material of which the insert is made preferably possesses natural elasticity or resilience so that it may be retained in the groove by its own elasticity and will, of course, be further held in place by the front plate of the lock through which the bolt head extends.

One object of the present invention is to provide a new and improved latch bolt of such a character that friction between this bolt and the parts of the lock case or strike plate which it engages will be greatly reduced.

Another object of the invention is the provision of a latch bolt of such construction that it will require a relatively low closing effort to retract the bolt due to the low frictional characteristic of the surface of the bolt which engages the surrounding parts of the lock, and which bolt will also be wear-resistant so that the closing effort will not appreciably increase during use.

Still another object of the invention is to provide a latch bolt having a groove formed in the surface of all of the exposed sides of the bolt and an insert of a material having a low coefficient of dry friction so that the effort required to retract the latch will be reduced.

A still further object of the invention is to pr'ovidea door latch bolt of the character described above wherein an insert of a material having a low coefiicient of friction is provided at the exposed surface of the bolt head, the insert projecting slightly beyond the surrounding portions of the head and having a natural resilience or elasticity so that it will be automatically retained in position upon the bolt head.

To these and other ends the invention consistsin the novel features and combinations of parts to be hereinafter described and claimed.

In the accompanying drawings:

Fig. l is a plan view partly in section of a door lock provided with a bolt embodying my invention;

Fig; 2 is'a plan view of the bolt head;

Fig. 3 is a side elevational view thereof;

Fig. 4 is a sectional view on line 4- 4 of Fig. 3;.

Fig. 5 is a perspective view of the bolt head before the insert-has been secured thereon; and

Fig. 6 is a perspective view of the insert alone.

To illustrate a preferred embodiment of my invention I have shown in Fig. 1 of the drawings a portion of a door 10 adapted to close against a door jamb 11. Within a bore in the face of the door is mounted a latch case 12 in which is slidably mounted a bolt comprising a bolt head 14, and a bolt stem 15 secured thereto in the usual manner. As will be understood the stem projects rearwardly into the case 12 so that the bolt may be retracted in the usual'manner by one or both of the knobs. 16.

As shown, the case 12 is provided with an opening 17 through which the bolt projects, and usually a face plate 18- is provided at the front of the case of the latch, this face plate also being provided with an opening 19 through which the bolt head extends in order that the latter may be projected through an opening 20 in a strike plate 21 secured to the door jamb.

The bolt head, as shown more especially in Figs. 2 and 3, is provided with a front surface 22, a beveled surface 23 which in the usual lock is adapted to engage the strike plate so that the bolt is cammed rearwardly into the case upon the closing of the door, and a back or security surface 24 which usually engages the edge of the opening in the strike plate to hold the door in closed position. It will be obvious that when the door is closed, if the beveled surface 23 engages the strike plate, the security surface 24 would be caused to engage the edge of the opening 19 in the face plate of the lock and bear frictionally against this edge.

As shown more especially in Figs. 4 and 5, a groove or recess designated at 26 is formed in the three sides of the bolt head previously described, that is, the front side, the beveled side, and also the back or locking surface. This groove is also extended to the inner face of the bolt head, as shown at 27 and 28, so that it extends over a portion of the inner face adjacent the front and security surfaces. This groove is relatively shallow and, as will be hereinafter explained, is adapted to receive an insert which is of a thickness to project slightly beyond the surfaces of the bolt head, and, therefore, constitute the part of the bolt head which engages the adjacent surfaces of the strike plate and lock.

This insert is shown in Fig. 6 and comprises a front portion 29 adapted to lie in the groove at the front surface of the bolt head, a portion 39 adapted to lie in the groove at the beveled portion of the bolt head, and a back portion 31 adapted to lie in the groove at the locking surface of the bolt head. It is also provided with inwardly and oppositely projecting free ends 32 and 33 adapted to lie in the grooves 27 and 28 at the inner face of the bolt. It may here be noted that the thickness of this insert is slightly greater than the depth of the groove 26 so that I the outer surface of the insert will project beyond the ad'- jacent surfaces 22, 23 and 24 of the bolt head, as shown in Fig. 2. Therefore, this outer surface of the insert becomes the striking surface which engages the door strike 21, and also the locking or back surface which engages the edge of the opening in the strike, and also the edge of the opening in the face plate of the door lock.

This insert will preferably be formed of a material hav- 4 ing a natural low coefficient of dry friction and a quality of surface oiliness or lubrication so that it will slide with relative ease over the lock and strike surfaces which it engages. It will also be of wear-resisting material and its quality of surface lubrication will assist in its wear resistance so that it will not only move with relatively low friction so as to require a relatively small effort to retract the latch bolt when the door is closed, but it will also resist wear so that it will still operate efliciently and with low friction after a long period of use.

The insert may be formed from such material as a polyamide (nylon), irradiated polyethylene, fluorocarbons and chlorinated fiuorocarbons. As formed, it will preferably possess natural resiliency or elasticity so that when shaped, as shown in Fig. 6, the free ends may be slightly spread so that it may be mounted in the grooves 26, 27 and 28, as shown in Fig. 4, and will be held in place by ,its natural resilience and by the shoulders on the bolt head at each side of the groove 26. After the bolt is mounted in the case, the insert will, of course, be additionally retained by its engagement with the front plate 18 of the lock case.

Tests have shown that the use of an insert of this kind so reduces the friction between the moving parts of the mechanism that the force required to close the door is considerably less than when a standard brass bolt is employed. For instance, a test showed that a standard brass bolt working against a brass strike required a closing force of 4.0 pounds, while a bolt having a polyamide insert required only 2.6 pounds in the same fixture. Moreover, after a million latching cycles, the resistance of the brass bolt has increased due to wear so that it required a closing force of 7.4 pounds, while the bolt with the insert according" to the present invention required a closing force of only-2.7 pounds after the same number of operations.

While I have shown and described a preferred embodiment of my invention, it will be understood that it is not to be limited to all of the details shown, but is capable of modification and variation within the spirit of the invention and within the scope of the claim.

What I claim is:' A'latch bolt for; doors comprising a bolt head adapted to cooperate with a strike plate, said head having front and back substantially parallel faces, an outer beveled face joining said front and back faces, and an inner face, a stem secured 'to the bolt head at its inner face, said stern being smaller'than said face to leave a considerable portion of the latter exposed, a groove formed in the front, back and beveled faces of the head of a width less than that of the head to provide a side shoulder on each side of the groove, said groove being extended a short distance over the inner face of the head at both edges thereof and terminating in end shoulders spaced from the bolt stem, an insert of generally U-shaped form seated in said groove, the thickness of said insert being greater than the depth of the groove whereby the insert projects from the front, back and beveled faces of the bolt head to provide a wear surface to engage a door strike, said insert being provided 'with inturned end portions at its free ends seated in said groove extensions and abutting against said end shoulders, said insert being of wear-resistant material having a low coetficient of friction and being resilient whereby it is held in place by its resilience and said shoulders.

eferences Cited in the file of this patent UNITED STATES PATENTS 1,194,636 Joy Aug. 15, 1916 2,033,079 Lohrs Mar. 3, 1936 2,159,315 Blue May 23, 1939 2,246,086 Austin June 17, 1941 2,499,165 Roethel Feb. 28, 1950 

